Abstract
We investigate a stationary pair production cascade in the outer magnetosphere of an isolated, spinning neutron star. The charge depletion due to global flows of charged particles, causes a large electric field along the magnetic field lines. Migratory electrons and/or positrons are accelerated by this field to radiate gamma-rays via curvature and inverse-Compton processes. Some of such gamma-rays collide with the X-rays to materialize as pairs in the gap. The replenished charges partially screen the electric field, which is self-consistently solved together with the energy distribution of particles and gamma-rays at each point along the field lines. By solving the set of Maxwell and Boltzmann equations, we demonstrate that an external injection of charged particles at nearly Goldreich-Julian rate does not quench the gap but shifts its position and that the particle energy distribution cannot be described by a power-law. The injected particles are accelerated in the gap and escape from it with large Lorentz factors. We show that such escaping particles migrating outside of the gap contribute significantly to the gamma-ray luminosity for young pulsars and that the soft gamma-ray spectrum between 100 MeV and 3 GeV observed for the Vela pulsar can be explained by this component. We also discuss that the luminosity of the gamma-rays emitted by the escaping particles is naturally proportional to the square root of the spin-down luminosity.
Similar content being viewed by others
References
Beskin, V.S., Istomin, Ya.N. and Par’ev, V.I.: 1992, Sov. Astron. 36(6), 642.
Cha, A.N., Sembach, K.R. and Danks, A.C.: 1999, ApJ 515, L25.
Cheng, K.S., Ho, C. and Ruderman, M.: 1986a, ApJ 300, 500.
Cheng, K.S., Ho, C. and Ruderman, M.: 1986b, ApJ 300, 522.
Chiang, J. and Romani, R.W.: 1992, ApJ 400, 629.
Chiang, J. and Romani, R.W.: 1994, ApJ 436, 754.
Daugherty, J.K. and Harding, A.K.: 1982, ApJ 252, 337.
Daugherty, J.K. and Harding, A.K.: 1996, ApJ 458, 278.
Dermer, C.D. and Sturner, S.J.: 1994, ApJ 420, L75.
Dyks, J. and Rudak, B.: 2003, ApJ 598, 1201.
Dyks, J., Harding, A.K. and Rudak, B.: 2004, ApJ 606, 1125.
Fierro, J.M., Michelson, P.F., Nolan, P.L. and Thompson, D.J.: 1998, ApJ 494, 734.
Goldreich, P. and Julian, W.H.: 1969, ApJ 157, 869.
Harding, A.K., Tademaru, E. and Esposito, L.S.: 1978, ApJ 225, 226.
Hirotani, K.: 2000a, MNRAS 317, 225 (Paper IV).
Hirotani, K.: 2000b, PASJ 52, 645 (Paper VI).
Hirotani, K.: 2001, ApJ 549, 495 (Paper V).
Hirotani, K. and Shibata, S.: 1999a, MNRAS 308, 54 (Paper I).
Hirotani, K. and Shibata, S.: 1999b, MNRAS 308, 67 (Paper II).
Hirotani, K. and Shibata, S.: 1999c, PASJ 51, 683 (Paper III).
Hirotani, K. and Shibata, S.: 2001a, MNRAS 325, 1228 (Paper VII).
Hirotani, K. and Shibata, S.: 2001b, ApJ 558, 216 (Paper VIII).
Hirotani, K. and Shibata, S.: 2002, ApJ 564, 369 (Paper IX).
Hirotani, K., Harding, A.K. and Shibata, S.: 2003, ApJ 591, 334 (Paper X).
Kanbach, G., Arzoumanian, Z., Bertsch, D.L., Brazier, K.T.S., Chiang, J., Fichtel, C.E., Fierro, J.M., Hartman, R.C. et al.: 1994, A&A 289, 855.
Mestel, L.: 1971, Nat. Phys. Sci. 233, 149.
Pavlov, G.G., Zavlin, V.E., Sanwal, D., Burwitz, V. and Garmire, G.P.: 2001, ApJ 522, L129.
Romani, R.W.: 1996, ApJ 470, 469.
Romani, R.W. and Yadigaroglu, I.A.: 1995, ApJ 438, 314.
Scharlemann, E.T., Arons, J. and Fawley, W.T.: 1978, ApJ 222, 297.
Sturner, S.J., Dermer, C.D. and Michel, F.C.: 1995, ApJ 445, 736.
Takata, J., Shibata, S. and Hirotani, K.: 2004, MNRAS 348, 241.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Hirotani, K. Gamma-Ray Emission from Pulsar Outer Magnetospheres. Astrophys Space Sci 297, 81–91 (2005). https://doi.org/10.1007/s10509-005-7578-x
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/s10509-005-7578-x